Galvez Thierry, Teruel Mary N, Heo Won Do, Jones Joshua T, Kim Man Lyang, Liou Jen, Myers Jason W, Meyer Tobias
Department of Chemical and Systems Biology and Bio-X Program, Stanford University School of Medicine, Stanford, CA 94305, USA.
Genome Biol. 2007;8(7):R142. doi: 10.1186/gb-2007-8-7-r142.
Iron uptake via endocytosis of iron-transferrin-transferrin receptor complexes is a rate-limiting step for cell growth, viability and proliferation in tumor cells as well as non-transformed cells such as activated lymphocytes. Signaling pathways that regulate transferrin uptake have not yet been identified.
We surveyed the human signaling proteome for regulators that increase or decrease transferrin uptake by screening 1,804 dicer-generated signaling small interfering RNAs using automated quantitative imaging. In addition to known transport proteins, we identified 11 signaling proteins that included a striking signature set for the phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3)-target of rapamycin (mTOR) signaling pathway. We show that the PI3K-mTOR signaling pathway is a positive regulator of transferrin uptake that increases the number of transferrin receptors per endocytic vesicle without affecting endocytosis or recycling rates.
Our study identifies the PtdIns(3,4,5)P3-mTOR signaling pathway as a new regulator of iron-transferrin uptake and serves as a proof-of-concept that targeted RNA interference screens of the signaling proteome provide a powerful and unbiased approach to discover or rank signaling pathways that regulate a particular cell function.
通过铁-转铁蛋白-转铁蛋白受体复合物的内吞作用摄取铁，是肿瘤细胞以及非转化细胞（如活化淋巴细胞）中细胞生长、活力和增殖的限速步骤。尚未确定调节转铁蛋白摄取的信号通路。
我们通过使用自动定量成像筛选1804个由Dicer产生的信号小干扰RNA，在人类信号蛋白组中寻找增加或减少转铁蛋白摄取的调节因子。除了已知的转运蛋白外，我们还鉴定出11种信号蛋白，其中包括一组针对磷脂酰肌醇-3,4,5-三磷酸（PtdIns(3,4,5)P3）-雷帕霉素靶蛋白（mTOR）信号通路的显著特征蛋白。我们表明PI3K-mTOR信号通路是转铁蛋白摄取的正向调节因子，它增加了每个内吞囊泡中转铁蛋白受体的数量，而不影响内吞作用或循环速率。
我们的研究确定了PtdIns(3,4,5)P3-mTOR信号通路是铁-转铁蛋白摄取的新调节因子，并证明了对信号蛋白组进行靶向RNA干扰筛选为发现或排序调节特定细胞功能的信号通路提供了一种强大且无偏见的方法。
